1. Field of the Invention
The technical field of the invention relates to methods of measuring morpho-geometrical parameters of a person wearing eyeglasses. By way of example these parameters may include the pupillary distance PD, the height H between the pupil and the bottom edge of the lens, the pantoscopic angle ΘP, i.e. the angle of inclination of the lenses relative to the facial plane of the person, the distance DVO between the eye and the lens V, and also the center of rotation CRO of the eye. It is essential to know these parameters in order to personalize a pair of eyeglasses properly, in particular with progressive lenses.
2. Description of Related Art
Methods also exist enabling some of these morpho-geometrical parameters to be measured. A first category of such methods make use of a vertical measurement column of large size with a camera being adjusted to the height of the eyes, the person wearing the eyeglasses looking at their own reflection in a mirror. That type of equipment is very bulky and thus requires premises of large size for taking the measurements, and it is not very flexible in use insofar as it cannot be moved easily in order to refine measurement, nor can it be broken up into separate elements in order to adapt to a given situation.
A second category of methods involves equipment of smaller size, in particular suitable for being placed on a table, but requiring a measurement protocol and positioning of the person wearing the eyeglasses that are most constraining. That type of method requires the person to adopt a very particular position for the head, and requires a clip to be applied to the eyeglass frame, the clip being provided with a rocker beam. A first step then consists in causing the person to adopt a natural posture, with the rocker beam then being blocked so as to fix the angle between the clip and the rocker beam, this angle corresponding to the pantoscopic angle. During a second step, the person wearing the eyeglass frame and its clip looks at a camera arranged above a screen. The person needs to tilt the head so that the blocked rocker beam is perpendicular to the axis joining the eyes and the camera. Such a method requires adjustments that are complex and accurate, and it requires a certain amount of dexterity on the part of the person wearing the eyeglasses, in order to be capable of taking up the correct position relative to the camera axis and to fix the position of the rocker beam accordingly.